For example, projection display apparatuses have more frequently been used in very dusty environments. In a very dusty environment, optical components may be contaminated and thus have reduced illuminance. Hence, a fine air filter is provided at the air intake of a display apparatus to remove dust so that air free from dust is fed into the display apparatus.
However, the fine air filter is likely to clog and disadvantageously requires frequent maintenance work in a very dusty environment. Related art for solving this problem is disclosed in Patent Literature 1 and Patent Literature 2 below.